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FTIR Evidence for Alcohol Binding and Dehydration in Phospholipid and Ganglioside Micelles
Author(s) -
Yurttaş Lale,
Dale Bruce E.,
Klemm William R.
Publication year - 1992
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/j.1530-0277.1992.tb01883.x
Subject(s) - chemistry , micelle , hydrogen bond , butanol , sialic acid , phospholipid , ganglioside , fourier transform infrared spectroscopy , molecule , membrane , organic chemistry , biochemistry , chemical engineering , aqueous solution , ethanol , engineering
We theorize that intoxicants and modern anesthetics bind at the membrane‐water interface and displace (dehydrate) bound water molecules by breaking the hydrogen bonds. We tested this hypothesis by examining the effect of butanol on the binding of water to the polar regions of lipids in reversed micelles. Understanding the mechanisms of intoxication requires studies in physiologically relevant systems such as systems containing sialoglycoconjugates, especially gangliosides, which concentrate in the synapses of neural tissue. Therefore, we compared butanol effects on phospholipid with effects on ganglioside. Hydrogen‐bond breaking activity of 1‐butanol was studied in reversed micelles made of dipalmitoylphosphotidylcholine (DPPC), ganglioside (GM 1 and GT 1b ) or the lipid mixture in a D 2 O‐CCl 4 medium. Fourier transform infrared spectroscopy (FTIR) data indicated that 1‐butanol binds to DPPC and to gangliosides. Adding GM 1 to the DPPC micelles introduces a new binding site for the alcohol. GT lb binds more butanol than GM 1 , because of more binding sites provided by extra sialic acid moieties. Spectral red shifts indicate that both water and butanol bind to the C = O group of sialic acid. Butanol partially releases the surface‐bound water by disrupting hydrogen bonds, as indicated by an appearance of a sharp new free OD stretching band of the released D 2 O molecules. However, control studies with lipid‐free systems in CCl 4 revealed that a free OD peak could occur from a deuterium exchange reaction between D 2 O and 1‐butanol(ol‐ h ). Thus, in lipid systems involving D 2 O and 1‐butan(ol‐ h ), deuterium exchange and partial release of water take place at the same time, and it is not possible to distinguish one from the other. Nonetheless, we could demonstrate butanol‐induced displacement of bound water with H 2 O + 1‐butan(ol‐ h ) and D 2 O + 1‐butan(ol‐ d ) in lipid‐free/CCl 4 and lipid/CCl 4 systems. Here, the alcohol also produced a new and large free OH peak that was larger than the OH peak produced when the same amount of butanol was used in the absence of water. This “free” water probably forms dimers and trimers with unbound butanol.